For example, an infusion system is disclosed in Patent Document 1 as a dosing mechanism for dosing a patient with liquid medicine (medicinal solution) filled in a medicine vessel. The infusion system has a pump module including a pump for feeding the medicinal solution from the medicine vessel to the patient. Patent Document 1 suggests that the pump module can be made disposable (throwaway).
Here, a sensor is provided for detecting a solution feeding state. An example of the sensor may include a pressure sensor. In the pressure sensor, a change of pressure inside a tube through which the medicinal solution is passing is detected by a change in diameter of the tube in order to grasp an event in which the tube has been closed.
However, when the pressure sensor as an example is applied to the configuration disclosed in Patent Document 1, the sensor must be attached to a tube extending to the outside from an apparatus including a pump and a mechanism for driving the pump. The tube outside the apparatus is prepared and connected to the apparatus by a medical institution. Therefore, the tube has a variation in diameter or hardness (ease of changing in diameter) due to a difference in manufacturing site. Thus, there is not always a fixed relation between a change of pressure inside the tube and deformation of the tube. In some tubes to be attached to the dosing mechanism, there is a case that the change of pressure cannot be detected accurately.